http://news.bbc.co.uk/2/hi/science/nature/3147769.stm
Last Updated: Wednesday,
13 August, 2003, 18:37 GMT 19:37 UK
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Climate
'destroying fish stocks'
CAPTION:
"Lake Tanganyika:
- Has 18% of the world's fresh water
- Yields 200,000 tonnes of fish annually
- Sardines down by about 50% since 1970s
A warming climate and not local fishermen is to blame for the
falling fish harvests in Lake Tanganyika, according to new research
findings published in the British journal Nature.
The shortfall threatens
the diets of the lake's shoreline countries
of Burundi, Tanzania, Zambia and the Democratic Republic of Congo.
The study was carried
out by a team of researchers led by Catherine
O'Reilly of New York's Vassar College.
Lake Tanganyika, the
second largest lake in the world, yields
200,000 tonnes of fish a year, an important source of food and
revenue for the shoreline nations.
The scientists found
out that the harvest of sardines,
the lake's main commercial fish, has declined by as much
as 50% since the 1970s.
Poor mix
This was caused mainly
by increased climate warming
- air temperatures over the lake have increased by about
1.5 degrees Celsius, while wind speeds have diminished.
With the temperature
of deeper water rising less dramatically,
this has resulted in less mixing of the layers, and algal growth
has dropped by 20%.
This in turn has led
to reduced food for several important
fish species, such as sardines.
As temperatures increase,
the decline in the lake's productivity
is expected to continue, according to Ms O'Reilly and her team
of researchers.
Scientists have already
predicted that central Africa's
Great Lakes region, where Lake Tanganyika is situated,
may face a temperature increase of up to 1.7 degrees Celsius
over the next 80 years, suggesting a greater shortfall in
fish harvests.
Other lakes
"The human implications
of such subtle, but progressive
environmental changes are potentially dire in this densely
populated region of the world, where large lakes are essential
natural resources for regional economies," the researchers
say.
They say the study
shows that global climate change has had a
greater impact on Lake Tanganyika than local human activity,
such as farming.
Lake Tanganyika, 650
kilometres long and 50 km wide,
contains 18% of the planet's fresh water.
The researchers say
that other lakes might be undergoing
similar changes.
